Monday’s medical myth: wearing tight undies will make you infertile

Tight underwear may increase scrotal temperature but there’s no evidence to show it reduces fertility. AAP

Most men have a preference for boxers or briefs, but which are better when it comes to fertility?

Many things can affect a man’s ability to make or transport sperm, including sexually transmitted infections, prostate and testicle infections, drug use, smoking, obesity and, perhaps surprisingly, heat.

Sperm are made in the testes (or testicles), a pair of egg-shaped glands that sit in the scrotum, in a lengthy and continuous process. It takes about 70 days for germ cells to develop into the mature sperm, found in semen, that can fertilise an egg.

Around one in 20 men have some kind of fertility problem, with low numbers of sperm in their ejaculate. But one in every 100 men produces no sperm at all.

Of the couples who present with fertility problems, almost half are due to fertility issues in the male partner only, or in both partners. It’s important to note, though, many men will still be able to father children naturally, even with have a lowered sperm count.

The location of the testes in the scrotum makes the testes vulnerable to trauma, but it serves a strategic purpose – to keep them around 2°C cooler than normal body temperature, which is required for the production of top-quality sperm.

Normally, the sweating of the scrotal skin serves as an “evaporative air cooling system” for the testes. But if it’s too hot and the scrotum can’t sweat, the testes will have trouble making sperm.

The scrotum needs to keep the testes 2°C cooler than the body to produce high-quality sperm. Gilberto Santo Rosa